The present invention relates to an electronic part assembly wherein electronic parts are assembled on a wiring board and connected to each other on the board to form an electronic circuit. More particularly, it relates to such an assembly capable of packaging many electronic parts in a small space by stacking up a plurality of wiring boards to form a three-dimensional structure.
In a typical example of a conventional assembly wherein electronic parts are assembled and connected to a wiring board to form an electronic circuit, a plurality of lead wires (hereinafter referred to as leads) of each electronic part are inserted respectively in holes of a printed wiring board which is formed by, for example, printing a wiring circuit on the lower surface of the printed wiring board and the inserted leads are soldered to the wiring board to make electric connections, thus forming an electronic circuit.
Recently, there has been an increase in surface-mounting type devices in which leadless-type electronic parts are mounted directly on the surface of a wiring board to provide electric connections of the parts. There is also a wiring board of the type having a wiring circuit on both the upper and lower sides thereof. In other words, there is also a double-sided board.
Further, to improve the packaging density for an increased number of electronic parts to be mounted, a double-sided board as shown in FIB. 2 is being utilized, wherein electronic parts 28 are mounted on both the upper 26 and lower 27 of a wiring board.
Recently such an IC as to have many pins compared with the conventional IC has been produced. Therefore, the IC is provided with leads densily so that a contact between adjacent leads tends to happen. For that reason, the IC having leads alternately bent upwardly and downwardly has been proposed. An assembly structure for mounting such IC on a wiring board, as shown in FIG. 3, wherein a supplemental wiring board 30 is disposed above a main wiring board 29 and an IC 31 is mounted and connected therebetween to form a circuit.
As described above, any of the conventional assembly is substantially a two-dimensional assembly wherein electronic parts are arranged on the same wiring board and each connected thereto with leads extending from its opposite sides. Accordingly, with an assembly structure in which intermingled are a low-profile part occupying a relatively large area of a wiring board and a high-profile part such as an electrolytic capacitor, the low-profile part occupies a fairly large packaging area while on the other hand the high-profile part occupies a space above the wiring board. Therefore, stacking up a plurality of assemblies of such type makes many useless spaces inevitably and lower the packaging density, thus resulting in hindrance to down-sizing of electronic apparatus.
An object of the present invention is to provide an electronic part assembly structure with an improved packaging density for contributing to down-sizing of electronic apparatus.